The actress, who just plunked down $5.1 million for an apartment at The Osborne across from Carnegie Hall, may find herself riding the elevator with a white-suited gentleman who died in 1947.

The ghost of Alfredo Taylor — an architect who designed the 1906 addition to the famed apartment house — is said to roam the building’s halls and ride the lift. It’s said he likes to dangle a watch fob from his hand.

But rumor has it Taylor is not the only ghost to call The Osborne Apartments home.

“I have a poltergeist!” said Naomi Graffman, who has lived at The Osborne with her husband, Gary, since 1962.

Graffman said sliding doors would open and close by themselves and a pot of water on the stove would boil without anyone turning on the burner. “We’d be standing in the hallway talking and the toilet would start to flush,” she said.

Graffman believes her spirited house guest is Johanna Gadski, a German-born mezzo-soprano who sang at the Metropolitan Opera before World War I. She lived at the time in The Osborne — in Graffman’s apartment.

Gadski, a red-haired practical joker, had to step down from the Met because she was German. She died in a car accident in Berlin in 1932.

Davida Deutsch’s first night in her Osborne apartment in 1971 was harrowing. Deutsch and her husband had heard rumors of a ghost and were so nervous, they left a broom near their bed in case they needed to ¬defend themselves against the apparition. Sure enough, they were startled awake by a loud bang in the night.

“We were scared to death,” said Deutsch, who put aside her fears and has become the building’s unofficial historian.

The Romanesque Revival apartment house — which went up between 1883 and 1885, several years before the famed music hall opened — became home to a long list of luminaries, including actresses Lynn Redgrave and Sylvia Miles, writer Fran Lebowitz, and Ira Levin, the author of “Rosemary’s Baby.” Phil Jackson, the president of the Knicks, is a current resident.

Chastain is buying a four-bedroom unit that once belonged to composer Leonard Bernstein, who sold it to cabaret singer Bobby Short.

John Coyne, the resident manager of the building, has heard the ghost stories, including the tales about Taylor.

“I haven’t come across anything strange,” Coyne said. “I don’t know if that means if he’s moved on or he’s moved out.”